This invention relates generally to the identification of quality and cost efficient medical providers, and specifically to computer software techniques and systems for estimating what the cost to treat a patient should be, based upon the condition of the patient and to the extent that any treatments or procedures impact the patient's health status.
Due to the geometric escalation of medical care costs, there is increased pressure on public policy makers to establish cost containment programs. For this reason state and Federal governments are beginning to adopt various case specific or case-mix reimbursement systems. The Social Security Amendments of 1983, (Public Law 98-21), introduced a diagnosis specific prospective payment system that has been incorporated into the Medicare reimbursement policies. Under this system, the amount of payment for a patient hospital stay is determined by a one of hundreds of government defined Diagnostic Related Groups ("DRGs") into which the patient stay is categorized based upon diagnoses and procedures performed. Hospitals are reimbursed according to a fixed schedule without regard to actual costs to the hospital in rendering medical services to the patient. It is expected that this same reimbursement policy will in time be extended to establish the level of reimbursement to other health care providers and/or from other government entities and insurers.
The DRGs represent a statistical, clinical classification effort to group together those diagnoses and procedures which are clinically related and have similar resource consumption. A DRG that is appropriate for a given hospital stay is selected, under the reimbursement system, by a particular set of patient attributes which include a principal illness diagnosis, specific secondary diagnoses, procedures performed, age, sex and discharge status (i.e., how the patient left the hospital, whether the patient was transferred, died, etc.). The principal diagnosis is that which caused the patient to be hospitalized, even though the patient may have even more serious problems, as would be indicated by secondary diagnoses. If a surgical procedure is performed, the DRG is determined primarily by that procedure. If no procedure is performed, the DRG is determined primarily by the principal diagnosis. The treatment of a patient during a single hospital stay is classified in only one DRG.
As shown in the few examples of DRGs given in Table I attached hereto, a fixed reimbursement factor (relative weight) is assigned to each DRG by the government. This determines the amount the hospital will be reimbursed for treatment of a patient that falls within the DRG, regardless of the hospital's cost or what the charges would have been for a non-Medicare patient. The more complex diagnoses or procedures that typically consume more resources should result in a higher paying DRG. (See the different relative weights in the example DRG's of Table I.) In addition to the reimbursement factor, each DRG has an average length of stay (LOS) in days assigned as another measure of the consumption of resources that is expected to treat a patient whose attributes cause that particular DRG to be selected.
There are currently 473 DRGs which cover all patients treated under inpatient conditions. These are set forth in the regulations of the Health Care Financing Administration. The example DRGs of Table I attached hereto are taken from those regulations. Since adoption of the system, regulations have been issued annually that make some changes in classification details to take into account experience under the system.
Under the current version of this reimbursement system, the hospital does not directly determine the appropriate DRG category for services rendered a Medicare patient. Rather, the hospital submits an appropriate Federal form (currently form UB-82) after discharge of the patient, which includes codes from a standard coding system to identify the primary and secondary diagnoses made, and any procedures performed, and gives patient information that is relevant to determining the appropriate DRG category, such as age and sex. As an alternate to using such a form, the coded information can be submitted on magnetic media, such as tape, in computer readable form. From this information, an intermediary reimbursing agent, or the Health Care Finance Administration itself, determines the proper DRG, and thus the amount of reimbursement.
The commonly used notation "ICD-9-CM" means the International Classification of Diseases--9th Revision, Clinical Modification, and refers to a coding system based on and compatible with the original international version of the ICD-9 coding system provided by the World Health Organization. The ICD-9-CM coding system is used in North America, and it is a classification of diseases, injuries, impairments, symptoms, medical procedures and causes of death. These codes are listed in detail in a publication of the Commission on Professional and Hospital Activities, Ann Arbor, Michigan, entitled "ICD-9-CM", Jan. 1, 1979. It is likely that the classification system will be revised and a 10th revision forthcoming within a few years. The techniques being described herein are not limited to a particular version of the ICD diagnosis and procedure classification system but rather will use whatever system is current at the time. As a shorthand reference to that system, the term "ICD" will be used hereinafter, unless a specific version is being discussed as an example.
The ICD coding system was designed for the classification of morbidity and mortality information for statistical purposes and for the indexing of hospital records by disease and operations for data storage and retrieval. The ICD codes are initially divided into Disease and Procedure sections. These sections are further divided into subsections which encompass anywhere from 1-999 three digit disease or 1-99 two digit procedure code categories. Within the three digit code categories there can be an additional 1 or 2 decimal digits to divide the codes into subcategories which further define the disease manifestations and/or diagnostic procedures. There are approximately 15,000 ICD codes. Only a portion of these are relevant for determining Medicare payments. The DRG Medicare payment system first involves the coding of diagnostic and procedural information into ICD code numbers by hospital medical records clerks before a patient can be assigned a DRG.
Each DRG is determined in part by an ICD code for the principal diagnosis, and ICD codes for each procedure that may have been performed. There are also ICD codes for identifying complications occurring during treatment, and the existence of any co-morbidities (i.e., secondary diagnoses of conditions other than the principal disease existing at the time of admission). These, as well as the patient's age, sex, and discharge status, determine a particular DRG for the patient.
It is possible that a large number of sets of ICD numbers or codes can lead to the same DRG. Table II attached hereto lists the ICD-9-CM codes that currently fall within each of a few of the DRGs that are used as examples in Table I. The existence of any one operative surgical procedure ICD-9-CM code listed under DRG 261, for example, will cause that DRG to be selected. The remaining DRG examples of Table II (numbers 31, 32 and 33) each have the same list of ICD-9-CM codes that will cause a DRG to be selected. A single one of these related DRGs is then selected based upon the age of the patient and whether there exists any complication or co-morbidity (referred to together as a "C.C." in the DRG definitions) as evidenced by an appropriate secondary diagnosis ICD-9-CM code.
A patient's age is a part of the definition of many of the DRG categories, as shown by the examples of Tables I and II. Pediatric patients (age 17 or less) and elderly patients (age 70 years or more) often fall into separate DRG categories that otherwise have the same textual definition. Where this occurs, the hospital is paid more for treatment of the older patient by assigning a higher paying DRG.
Also, the presence of a complication or comorbidity (C.C.) with a patient is a part of the definition of many DRGs. A patient with a complication or comorbidity is considered to be a sicker person for certain illnesses than one without a C.C. and the hospital is reimbursed more for those illnesses by classifying such a patient in a higher paying DRG. However, not all medically recognized complications or comorbidities are recognized by the DRG reimbursement system to have any effect on the payment to be made. The DRG Medicare system currently specifies about 3000 of the approximately 15,000 ICD-9-CM codes as effective to establish a C.C. and thus provide higher reimbursement. That is, if any one of these approximately 3000 ICD-9-CM codes appear as a secondary diagnosis on the patient discharge information, a C.C. is deemed to exist. Thus, if the patient is otherwise classified into a family of DRGs where the existence of a C.C. makes a difference, the higher paying DRG is selected from the family. For example, with regard to the family of DRGs 31, 32 and 33 of Tables I and II which have the same lists of principal diagnoses ICD-9-CM codes, both the patients age and the existence or non-existence of a C.C. determines which of the three DRG categories is selected for reimbursement purposes. It should be noted that the relative weight and mean length of stay (LOS) definitions of those three DRGs vary widely.
The actual reimbursement that a hospital receives for each patient involves the multiplication of the relative weight of the DRG (see Table I) with other factors set by the Federal government. These other factors are determined by statistical variables (e.g. cost data of that particular hospital for a period, the type of patients a hospital treats in relation to the hospital's resources expended for those patients, and the wage and cost of living index).
Computer software is available for calculating the appropriate DRG from the input codes that are provided by the hospital. A DRG Grouper System converts the ICD codes of a patient's stay, along with the other DRG related factors (age, sex, discharge status), are mapped into the corresponding DRG category. This is public information that is available at cost. One company manufacturing an enhanced DRG Grouper is the DRG Support Group, Ltd., a subsidiary of Health Systems International, Inc.
Because such a large proportion of hospital patients fall under the Medicare system (40% or more of the patients of some hospitals), the DRG system is extensively used. It is natural, therefore, that the system would also be used for health care management and evaluation purposes. However, it is widely recognized that the grouping of patients resulting from use of the DRG system does not have as high a degree of homogeneity as is statistically desirable. That is, the resource consumption of a population of patients, who all are classified into a single DRG, varies widely. The statistical deviation from the single mean length of stay (LOS) for most of the DRGs is large, apparently because the overall level of sickness of the patients so grouped varies widely. The sicker patients require more hospital resources to be devoted to them but the DRG Medicare system considers this only to a limited extent by selecting a DRG primarily from only a single principal diagnosis made or surgical procedure performed.
As a result, there have been many suggestions for refining the DRG system, or to go to a different system, in order to result in a more homogeneous grouping of patients. The reasons for doing so include the need to have data for monitoring hospital and physician performance, as well as improving the reimbursement system itself. The suggested approaches include many different ways to measure how sick a patient really is.
The primary variable in any patient population which must be taken into account before either mortality and morbidity rates or resource consumption can be addressed is that of the patient diagnosis. If a physician is asked to predict the mortality rate of a group of patients, the first question he or she will ask is "What is the diagnosis?". The expected mortality rates between a fractured wrist and cerebrovascular accident (stroke) are very different. The DRGs are a very adequate way of subdividing the patients on the basis of their diagnoses.
The second and crucial variable is that of the severity of the patient's illness within each of the various diagnoses. An example is that some myocardial infarctions (heart attacks) are fatal, and some go completely unnoticed by the patient, representing a wide variation in severity. The DRGs do not have the ability to adequately determine the acuity (severity) of the patient's illness within the diagnostic categories.
It is a primary object of this invention to provide a computer based technique and system for estimating the severity of patients' illnesses from hospital discharge data and other medical information, and for estimating the resources likely to be consumed in the course of providing medical service to patients, all with improved accuracy and convenience.